1. Field of the Invention
The present invention relates to an electrolytic cell having a cation exchange membrane. More particularly, it relates to an electrolytic cell which is formed by bonding a porous, gas-liquid permeable, electrode layer to a cation exchange membrane and is suitable for an electrolysis of an aqueous solution of an alkali metal chloride.
2. Description of the Prior Art
As a process for producing an alkali metal hydroxide by an electrolysis of an aqueous solution of an alkali metal chloride, a diaphragm method has been mainly employed instead of a mercury method in view of a prevention of a public pollution.
It has been proposed to use an ion exchange membrane in place of asbestos as a diaphragm to produce an alkali metal hydroxide by electrolyzing an aqueous solution of an alkali metal chloride so as to obtain an alkali metal hydroxide having high purity and high concentration.
On the other hand, it has been proposed to save energy in the world. From the viewpoint, it has been required to minimize a cell voltage in such technology.
It has been proposed to attain an electrolysis by a so-called solid polymer electrolyte type electrolysis of an alkali metal chloride wherein a cation exchange membrane of a fluorinated polymer is bonded with gas-liquid permeable catalytic anode on one surface and a gas-liquid permeable catalytic cathode on the other surface of the membrane (British Pat. No. 2,009,795). This method is remarkably advantageous as an electrolysis at a lower cell voltage because an electric resistance caused by an electrolyte and an electric resistance caused by bubbles of hydrogen gas and chlorine gas generated in the electrolysis, can be remarkably decreased which have been considered to be difficult to reduce in the electrolysis.
The contact of the gas-liquid permeable porous electrode with the cation exchange membrane is an important factor for the efficiency of the electrolytic cell in such solid polymer electrolyte type cation exchange membrane electrolytic cell. When a thickness of an electrode is non-uniform or a contact between the electrode with the cation exchange membrane is not satisfactory, a part of the electrode is easily peeled off whereby a cell voltage increases or the gas and the solution remain in the interfaces to cause the increase of the cell voltage. The desired advantages of the electrolytic cell are decreased or lost.